Piston for internal combustion motors



Aug.. 9, 1938. E. c. LONG PISTO FOR INTERNAL GOMBUSTION MOTORS Filed March 28, `193e;

2 Sheets-Sheet 1 Aug. 9, .1938.

Filed March 28, 1936 E. c. LONG` PISTON FOR INTERNAL COMBUSTION MOTORS 2 Sheets-Sheet 2 17229612321@ 'Zze/fa@ N @MM Patented Aug. 9, 1938 UNITED STATES PATENT OFFICE Y rls'roN ron, INTERNAL oonmUsrroN Morons 8 Claims.

This invention relates to pistons for internal combustion motors and pertains more particularly to pistons made of metal having a high coeiiicient of expansion, such as aluminumor aluminum alloys, such pistons to be used in cast iron cylinders having a lower co-eicient of expansion than the pistons.

The present invention is a furthering of the invention disclosed in my cao-pending application for Piston, iiled July 30, 1932, Serial No. 626,364, renewed July 6, 1937.

'I'he principal object of the invention is to provide a piston made of a relatively light material which can be fitted in a cold cylinder of a motor with a very small clearance and which will maintain this clearance substantially throughout the thermal changes of the motor without slapping or scoring of the cylinder. Another object of the invention is to provide a piston having a skirt with a flexible thrust side and an opposing solid thrust side, and with means extending from the solid thrust side, in a plane adjacent and above the pin bosses to the exible thrust side to substantially maintain the flexible thrust side with a minimum clearance between it and the cylinder wall.

A further object of the invention is to provide a strut piston of an improved interior construction to both simplify and aid the die casting oi the piston.

Other objects and advantages will appear as this description progresses and by reference to the drawings, in which:-

Figure l is a pin boss side elevation of this improved piston.

Figure 2 is a power thrust side elevation of the piston taken in thedirection of the arrow I1 in Fig. 1.

Figure 3 is a vertical sectional view taken approximately on the line III--III of Fig. 1.

Figure 4 is a vertical sectional view taken approximately on the line IV-IV of Fig. 2.

Figure 5 is a horizontal sectional view taken approximately on the line V-V of Fig. 3. l

Figure 6 is an inverted horizontal sectional view taken approximately on the line VI-VI of Fig. 4.

Figure 7 is aninverted horizontal sectional view taken approximately on the line VII-VII of Fig. 4.

Figure 8 is a horizontal sectional view taken approximately on the line VIII-VIII of Fig. 3.

Figure 9 is an open end elevation of Fig. 1 taken in the direction of the arrow IX, in Fig. l.

Referring to the several gures of the drawings, l the piston shown comprises a head ID having a (en. soc- 13) side wall H in which packing ring recesses l2 are formed, anddepended from the side wall` l i is the piston skirt i3.

The skirt i3 is provided with opposing thrust sides it and 15 and opposing pin boss sides 16 which are disposed at right-angles to the skirt thrust sides, and each carrying an inwardly extending pin boss il.

Formed integral with the inside of the head it and extending across the center of the longitudinal axis of the piston and at right-angles tothe pin boss sides i6, is a rib or web 18, said web also being integrally joined at its ends with the side wall l Il of the head and to upper parts of the skirt i3 on the thrust sides it and l5 thereof. 1

The inner or depending end of the web 18 is arch-shaped and in abutment therewith, is the tapered upper edge i9 of a strut Ell fitting in a similar formed groove 2li in the depending end of the web it, said strut 2t having a shape in conformity with the arch-shape of the depending end of the web 18.

The strut 2|) is of a material having a lower coeilicient of expansion than the material from which the piston is made, and is provided at each end with a pair of oppositely directed bent parts 22 which are embedded in the heavy or thicker parts 23a of the skirt it, best shown in Figs. 4,

5 and 7 of the drawings.

In the die casting of this improved piston, only a threeepiece core is required. rlhese comprise a central core A iitting between the pair of parallellng vertical lines illustrated in Fig. 3, and said cores B occupying'the space on each side of the core A. 'I'his improved structure of piston therefore provides a simplication of coring and die casting in that the side cores B are iirst located in position in the mold, and the central core A supporting the strut 2t is then positioned between the side cores B.

Obviously, as the central core A and side cores B will determine the conforming shape of the interior of the piston, and the outer shells of the mold (not shown) will determine the 'outside shape or 'contour of the piston, when the metal is poured, the conforming shape particularly with respect to the interior of the piston, will be that shown in Fig. 3.

After the molding operation of the piston, the central core A can be conveniently dragged or 50 dropped away from the piston head Il), the web it and the strut 20 which is in abutment with the depending end of the web, and the side cores B are then moved inwardly into the space previously occupied by the core A and are then dropped from the molding. The die cast piston to all appearances is then of a conventional trunk type piston.

In the molding of the piston, the pin boss sides I6 are provided with reliefs or inserts 23, as shown in several figures of the drawings, and the exterior of the piston and/or the thrust sides I4--I 5 and head II) are machine turned and the pin bosses II are bored. Saw cuts are then made in the thrust side I4 of the skirt I3 which is the power thrust side of the skirt, to provide the pair of side disposed inverted L-shaped slots 24, shown in Fig. 2, the horizontal leg 25 of each slot being extended towards eachother and formed in the lower piston ring recess 26, and the vertical leg 21 of each slot 24 being formed at the end of respective pin boss sides. This form of slotting provides an integral part between the extending ends of the legs 25 of respective L-shaped slots 24. which connects the thrust side I4 of the skirt with' the side wall I I of the head IIJ ofthe piston.

The thrust side I5 which is the compression thrust side of the skirt I3, is separated from the side Wall II of the head I0 by an inverted U- shaped slot 28 which is formed by saw cutting the horizontal leg 29 of the slot 28 in the lower piston ring recess 26, and each vertical leg 30 of said slot is saw cut through the skirt at the end of respective pin boss sides I6. In saw cutting the slot 29 a portion of the depending end of the web I8 above the strut 20, is severed, in the manner best shown in Fig. 4. 'I'he thrust sides I4 and I5 of the piston skirt are then ground and the piston is then complete and ready for assembly.

The piston when ready for mounting in a cylinder of an internal combustion motor, is provided with a minimum oi' clearance on a diameter across the thrust sides I4-I 5 of the skirt to eliminate piston slap in operation when the motor is cold. When the piston expands due to heat and particularly the head I0 which will receive the greatest degree of heat, (said head being of less diameter than the skirt in order to allow for head expansion) any expanding outward movement of the side wall II of the head will move the compression thrust side I4 therewith, by reason of it depending from the head side wall, and this outward movement will be transferred tothe strut 20 and a' drawing and/or holding-in effect will be given to the tongue portion 3| provided by the U-shaped slot- 23 in the compression thrust side I5 of the skirt I3. In addition, outward movement or normal expansion across the thrust sides I4--I5 will be prevented on account of the strut 20 having a less co-efilcientof expansion than the material of the piston.

The curvature of the strut 20 (Fig. 4) imparts to it a degree of longitudinal resiliency which allows adjustment of the strut relatively to the metal of the piston during cooling thereof after casting. At such time, as the piston body contracts with relation to the strut, (which is ordinarily not even pre-heated), the web I3 tends to contract (vertically) away from the strut, while the contraction of the head I0 and skirt I3 applies compression pressure to the bent ends 22 of the strut, which may under this pressure bow upwardly. The desired location of the embedded ends 22 of the strut 20 in the non-ferrous metal is thus not disturbed, and a tightly cast joint between such metal and the ends of the strut is assured. When the tongue portion 3| of the skirt is thereafter sawed out, compression strains which have been applied to the strut in the manner described is somewhat relieved, and the Strut reassumes its intended shape and proportions. holding the tongue portion in the desired relative position as the curved strut will still retain residual compression strains after the skirt has been slotted for providing the flexible compression thrust side I5. This holding of the tongue portion is also rendered somewhat resilient by virtue of the curvature of the strut, which resiliency is oi' benet not only in itself, but because the yieldability thereby given the ends of the strut, cushions and so .tends to prevent loosening thereof by any impacts which may be applied thereto in service. l

The residual or retained compression strains on the curved strut 20 is occasioned by the slots 21 and 30 falling short of extending to the bottom of the skirt I3 and the retained compression strains on the curved strut will cause it to receive side support from the web I8 by reason of the high point or apex of the strut being held in the groove 2I in the edge of the Web I8.

With the application and use of a single centrally disposed strut 20 through the longitudinal axis of the piston, the material of the skirt and particularly respective thrust sides I4-I5, can uniformly expand circumferentially away from each side of the strut on each end in the extending directions of the embedded bent parts 22 of the strut, without distortion.

From this disclosure, it is obvious that the original small clearance given the piston skirt across the thrust side diameter will remain substantially unchanged throughout the temperature ranges developed in the use of this improved piston.

The pin boss sides I6 of the skirt I3 in addition to being provided with reliefs 23, are each provided at their lower ends with a cut-away part 32 which extend upwardly to respective pin bosses I'I. Expansionv of the piston across the pin boss sides will therefore not become effective to cause frictional scoring of the pin boss sides on the cylinder wall and at the same time the cut-away portions 32 will provide yieldability for the lower ends of respective thrust sides I4-I5.

Having thus described the invention so that those skilled in the art will be able to practice the same, what I desire to secure by Letters Patent is defined in what is claimed, it being understood that various changes in the piston shown and described above in detail and not amounting to invention, may be made without departing from the spirit and scope of my invention.

What I claim is:-

1. A piston comprising a head, a skirt having a resilient thrust side and a rigid thrust side, a centrally disposed web integral with the head and extending thereacross, and a strut of material different from the skirt and substantially abutting and paralleling said web and connected at its ends to said thrust sides.

2. A piston comprising a head, a skirt having a resilient thrust side and a rigid thrust side, a centrally disposed web extending across the head, and a strut connected at its ends to said thrust sides and substantially abutting with said web.

3. A piston comprising a head, a skirt having a resilient thrust side and a rigid thrust side, a centrally disposed web extending across the head, and a strut of a material having a low co-eiiicient of expansion, connected at its ends to said thrust sides and contacting intermediately with said web.

4. A piston comprising a head having a side wall, a skirt having a resilient thrust side and a rigid thrust side, said rigid thrust side depending from the side wall of the head, astrut of material different from the skirt disposed across the longitudinal axis of the piston and having its ends embedded in the upper ends of respective thrust sides, and a centrally disposed web integral with the head and substantially abutting and paralleling said strut.

5. A piston having a head including a ring land, a skirt, a centrally disposed web integral with andextending across the inside of the head and having its ends joined with' the ring land, pin bosses having axes transverse to the web, and a curved strut in substantially'paralleling abutment with the web and connected at its ends to opposing sides of the skirt.

6. A piston having a head including a ring land, a skirt, a' centrally disposed arched web integral with and extending across the inside of the head and having its ends Joinedwith the ring land and one end of said web joining with an upper part of the skirt, pin bosses having axes transverse to the web. and an arched vstrut dis ylng its ends joined with the ring land, said webv being grooved on its depending end, and a strut having an edge seated in the groove of said web and connected at its ends to opposing sides oi? the l piston. l

8. A piston having a head including a ring land, a skirt, a centrally disposed depending web integral with and extending across the inside of the head and having its ends joined with the ring land, said web being curved and grooved on its depending end, and a strut having its upper edge seated in the groove of said web and connected at its ends to opposing sides vot the skirt.

ELMER C. LONG.

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